An electronically controlled transmission system is commonly referred to as a “shift-by-wire” transmission system. In some shift-by-wire automatic transmission systems, an input shaft outwardly projects from a transmission gear housing and is rotated to shift gears in the transmission. The transmission input shaft is rotated by an electric actuator coupled to the input shaft. The electric actuator selectively rotates the transmission input shaft in response to an input signal from a manually operated gear shifter or gear selector. The gear selector is typically a lever but can alternatively be in other forms such as push buttons.
Typical electric actuators of shift-by-wire transmission systems have an electric motor which rotates the device repeatedly back and forth until the transmission input shaft is in the exact gear position that is desired. This can result in relatively slow and inaccurate shifting. Accordingly, there is a need for an improved electric actuator for shift-by-wire automatic transmission systems.